Efficiency extractors

If a rapid, reciprocating motion of relatively short amplitude is applied to the liquid contents of an extraction column, the column is said to be pulsed. The agitation thus provided has been found to give improved extraction rates. Devices of this sort were suggested as early as 1935 (VI), but it was not until the atomic energy programs in the United States and Great Britain developed a need for efficient extractors of low... 

Overheating the microwave oven tends to result in boiling or excessively rapid evaporation of fluids such as ethanol used for dehydration, formaldehyde employed for fixation, and the antigen retrieval fluid. As a result, flammable and/or toxic materials are released in the microwave oven. Even without overheating, vapors are produced because containers are kept open in the oven to prevent pressurization. Transparent microwave containers should be used, fluid volumes should be -100ml. Microwave ovens with attached efficient extractor fans are commercially available, as are microwave ovens with temperature probes. To avoid possible exposure to toxic vapors, the face should be turned away when the oven door is opened (Horobin and Fleming, 1990). The oven door should not be opened or closed to turn the microwave power on and off. 

Other crown ether ionophores have been developed as ion sensors. The first reports of crown ethers as dyes appeared in the 1970s. These derivatives of benzo-15-crown-5 undergo a color change when bound to specific ions and can be used as efficient extractors for ions from aqueous solution. Numerous other chromoionophores have also been prepared and were reviewed by Takagi (1984). 

The RDC has a moderate throughput typically in the range of 20 to 35 mV(h m ) [500 to 850 gal/(h ft )j, and it can be turned down to 20 to 35 percent of the design rate. However, the relatively open arrangement leads to some bacWixing and results in only moderate mass-transfer performance. As a consequence, some RDC columns are being replaced by more efficient extractor designs. The RDC can be... 

Plot of extraction efficiency versus pH of the aqueous phase for the liquid-liquid extractor of the molecular weak acid in Example 7.16. 

Overall Stage Efficiencies The mixer-settler extractors described have generally produced overall stage efficiencies in excess of 80 percent, usually nearly 90 to 95 percent. 

One of the chief characteristics of the Karr column is its high-volumetric efficiency when compared to other extractors. Volumetric-efficiency is defined as ... 

Karr, Holmes, and Cusack have given comparisons of the Karr column volumetric efficiency with other types of extractors. In Table 15-10 are data showing the values of HETS and volumetric efficiency over a range of column diameters from 1-36 in (0.025-0.9 m) Fig. 15-51... 

FIG. 23-38 Efficiency and capacity range of small-diameter extractors, 50 to 150 mm diameter. Acetone extracted from water with toluene as the disperse phase, V /V = 1.5. Code AC = agitated cell PPC = pulsed packed column PST = pulsed sieve tray RDC = rotating disk contactor PC = packed column MS = mixer-settler ST = sieve tray. (Stichlmair, Chem. Ing. Tech. 52(3), 253-255 [1980]). 

If the desired product is fairly water soluble, simple extraction into organic solvents may not be an efficient means of recovery. In that case, continuous extraction of the aqueous solution with an organic solvent may be necessary to effect the recovery. Either of two types of apparatus are normally employed, and the correct design depends on the density of the organic solvent. For solvents less dense than water, the apparatus should be set up as in Fig. A3.11a. The barrel of the extractor is charged with the... 

Extractors with mechanical agitation, such as mixer-settlers, Kuhni columns, York-Schiebel columns, etc., should be avoided as much as possible. Up to seven theoretical stages packed extraction columns can be conveniently adopted. Sieve-plate extractors can be used up to 20 stages. When a very efficient extraction has to be carried out with expensive solutes, and for reasons of material stability and requirements of low expensive product inventory, we may have to use centrifugal extractors or hollow-fibre extractors. 

Homogenizer mechanically shaken with an appropriate Soxhlet solvent for a set period of time, extractor Extraction efficiency may be improved by... 

Contimious liquid extraction techniques are used when the sample volume is large, the distribution constant is small, or the rate of extraction is slow. The efficiency of extraction depends on many factors including the viscosity of the phases, the magnitude of the distribution constant, the relative phase volumes, the interfacial surface area, and the relative velocity of the phases. Numerous continuous extractors using llghter-than-water and heavier-than-water solvents vee been described [3,2 7,42,73,74]. Generally, either the ligi Pr or heavier density... 

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